Sintered hard metal alloy for tools and similar articles



Patented May 12, 1936 i j i p N w sIN'rEREn H RD. METAL ALLOY Fox TOOLS ANDS IMILABLABTICLES] Karl Becker,-Berlin-Lichterfelde st,*Germany,* assignor to Wolfram & MolybdaenwL-Ga 1..

Zurich, Switzerlandv I v uni-ED No Drawing. Application November "j6,"-,1933,

j SerialNo. 696,919: In Switzerland November 18, 1932 I '2 Claims." (Cl.'75- -136) This invention, relates to the manufactureof of hard; titanium compoundssuch as titanium. hard alloys for tools and other similar articles, carbide and titanium nitridein an amount up to j the said alloys being of thev kind in which tung- 50 percent of the total alloy, sten carbide, is, the principal constituent whilst The present inventionhas-for its object toef there is also presentan auxiliary metal; of much fect still further improvementsin the properties lower melting point than the tungsten carbide, which are essential for the quality of meta'lsfior comprising one or more of the metals iron, nickel cutting tools, and forthis purpose the sintered or cobalt v I I alloys according tothe present inventionjcomprise Heretofore it has beenproposed to improve the at least 50 per cent of tungsten; carbide, aquan- [0 properties of sintered hard alloys having a tungityup to 20 per cent of one or more of the metals Stem carbide base and also containing an auxiron, cobalt and nickel, and a quantity of 2 to 30 iliary metal suchas iron, cobaltor nickel have her. e t of hard miXedcrystalsof carbides or inga substantially lower melting'point than that carbides and nitrides for'med from a carbide or of the tungsten carbide by the addition oi an: n tr d f a m t l. f thefou f h group of. the

5 other hard carbide or carbo-nitride having a high periodic system and a carbide or nitride. orla metal l5 melting point. Thus it has been proposed to add of the fifth group of theper'iodicvsystem. The to a mixture comprising tungsten carbide and up hard, mix dn l f carbides carbides n to per cent of an auxiliary metal of lower meltnitrides should be completely formed before their jng p mtr asfliron, b lt or nickel oneor addition to the other constituents of the alloy, I

20 more carbides of tantalum, niobium or vanadium namely un en ideflandro e; o m b y '20 in quantities of 0.01 t so percent and tofwork a s iron, alt r ni kel. l v up this mixture further in the usual way. Eur- Itis known that mixturesof many hard subther, tool alloys have been proposed comprising stances and compounds having a high melting ,a 'sintered product containing at least two car- PO DEQmO pa l r of c tai d x- '25 bides of tungsten, molybdenum, boron, silicon, turesor even carbide lnitride mixtures, show con.- titanium, zirconium and vanadium which are obsiderable solubility QrIOI'm'a. con d b mo nt tained entirely in the form of mixed crystals by of mixed crystals withone another. Infcertain heating to a suificient, extent and an addition individual cases, wherethereis a close relationamounting to 3 to. 20, per cent of one or more shipoffthe lsubstancesasregards structure,,an

metals such as nickehcobalt and chromiumflthe unlimited flawlessf formation" of 'mixed crystals 30 I most favourable results were stated to have been may result. Furthermore; it is known that by the obtained with mixed crystals of the system molyb-' formation of rmxed crystals the hardness or alloys denum' carbide-tungsten carbide. Moreover, is as a rule very considerably increased. This metal carbo-nitrides have been proposed for imis also the case with the hard carbide systems parting a high degree of hardness toalloys, the and carbide nitride systems utilized in the pro- 35 carbo-nitrides with or without nitrides of metals duction of the alloys accordi g to the present in-. or metalloids being added to the various metals or vention, for example with the Systems Tic-TaC. alloys as constituents; an example of this pro- TiC''NbC, TiC--VC, ZrC-TaC, ZrC--N'bC,. f cedure was the increase of the solidity and hard- ZrC-VC, HfCTaC, HfC-NbC; HfC- VC,

40 ness of known hard alloys consisting chiefly oi TiN-TaC, TaNTlC and similar mixtures. The 40 tungsten or molybdenum carbides by additions maximum hardness is mostly present, although thereto of carbo-nitrides-in this way for not always, when the two constituents are mixed instance there was produced a hardand rein equimolecular propor i n for example in the sistant alloy comprising tungsten carbide as system TaC-TiC in the proportion .01 23.7 per principal constituent and small percentages of cent by weight TiC to 76.3 per cent by weight' chromium carbo-nitride, tungsten carbo-nitride, TaC. The increase in hardness is particularly cobalt and tungsten. There have also been pronoticeable when one component of the mixed posed hard metal alloys comprising zirconiumor crystal consists of a hard nitride, for example thorium carbide or both in a quantity not exin the system TiNTaC or TaN-TiC.

ceeding 20 per cent, cobalt up to 10 per cent and The production of hard alloys which, apart 50 tungsten carbide as the remainder. Lastly there from an addition up to 20 per cent'of one or more have been proposed sintered hard alloys consistof the metals iron, cobalt and nickel, consist exing of tungsten carbide, a metal of lower melting clusively of several carbide or carbide nitride point than that of the tungsten carbide in an mixed crystals, is possible per se, but by utilizing 1 amount of up to about 25 per cent and a mixture the hardness of the mixed crystals described by 55 adding them in present invmtion ,in quantities of 2 toBO .per cent to tungsten-carbide and one or more ,of theadditionai metals, iron, cobalt and, nickel o ofthe latter produces a substantial-lemme! the heat conductance which has proved to be favourable in practice.

It has likewise been found practical to an alloy of an iron metal with a metal with boron instead of one'or more additional metals of .the iron group, suchas lron,'jcoba lt or nickel. It is particularly advisable. in this instance. to select molecular proportion, so that intermetallic Chm! pounds result. Such compounds, for example of the cobalt or nickel with denum are produced in that the molecular quantitles of the individual components corresponding to the chemical formula W00, Willa. MoCo, Mom as metal powder are thoroughly mixed and then aintered in an electric'furnacein a reducing 'at a temperature between'l200 and mo- C., which lies below their melting point. employing the borides cobalt or nickel are thoroughly mixed in the molecular proportion corresponding to the chemical formulae NiBp'CoB, NisBa, C0582, NiBa, C023 and sintered in a vacuum at a temperature between 800 and "1300 C. After these compounds have been produced, they are thoroughly mixed in quantities upto; with the other hard metal components, such as the tungsten carbide and the mixed [crystal formed from carbides'of metals of the 4th and 5th group of the periodic system, and-afterthe powders have been pressed,sinteredat a'temperature between 14001 and 1700',C., slightly higher than the melting point of the additional metal no. a g v.

The toughness and strengthens not aifected by employing'the additional metal alloy. i The dendty and hardness of the hard metal alloy is, however, increased by the possibility of apply ing a highersintering temperature. If the sintering iscarried out, as usual, in a tubular coal -furnace through which hydrogen flows, the additional metal compounds, owing to the great mutual chemical afllnitylof their components, remain unchanged at sintering temper.-

4th, 5th or 6th group of the periodic system or I proportions and then heated for such a long period in a tubular coal furnace traversed by hydrothe components of the alloy in tungsten or. [molybsint'ered' during a period atures upto 1700' C. tion of the presence of tunfltencarbidaauchas is the case "for exumie tungstenis added to the tungsten manual-bide whereupon carbides form.

a in carrying outthe present invention in order to produce the hard mixed crystals desired the purest possiblecomponents, for example TiC' and TaC, are intimately mixed together in molecular lower tungsten ature. between 1500' C. and 2000 C. is-sumcient.

The mixed crystals, which remain at the room temperature after cooling on," are now added in a quantity of about 10 per cent by weight to a hard-metal powder-consistingof 95 per cent tungsten-carbide and 5 per cent cobalt. The mixture is ground in a known manner for a lengthy period in ball mills, pressed and finally of '1 to 2 hours at between 1400 C. and 1800 0., say about 1500' C.

in a tubular coal furnace traversed by hydrogen.

In some cases, a high temperature sintering in a nitrogen current or a hydrogen-nitrogen current or even in a gaseouscurrent charged with ammonia is suitable with subsequent annealing in a nitrogen'atmosphere between 1200 C. and: 1600 1. Sintered hard metal alloy for tools and'similar articles, consisting of atleast 50% tungsten carbide, up to %:cf an additional metalalloy of a metal of the'iron'group'. with boron, and 2 to of a hard mixed crystal of carbides of an element of the 4th group with an element of the 5th group of the periodic system. I

2. Sintered hard metal alloy for tools and similair articles, consisting of'at least 50% tungsten carbide, up to 25%' of additional metal of the iron group and 2 to,30% of a preformed hard mixed crystal of only one pair of carbides selected from the following group,namely:' TiC-NbC, ZrC-NbC, HfG-Nb'CQ'I-IfC-VC.

'wcoanot caused by the 

